title: A systematic approach toward stabilization of CagL, a protein antigen from Helicobacter pylori that is a candidate subunit vaccine.
abstract: An important consideration in the development of subunit vaccines is the loss of activity caused by physical instability of the protein. Such instability often results from suboptimal solution conditions related to pH and temperature. Excipients can help to stabilize vaccines, but it is important to screen and identify excipients that adequately contribute to stabilization of a given formulation. CagL is a protein present in strains of Helicobacter pylori (H. pylori) that possess type IV secretion systems. It contributes to bacterial adherence via α5β1 integrin, thereby making it an attractive subunit vaccine candidate. We characterized the stability of CagL in different pH and temperature conditions using a variety of spectroscopic techniques. Stability was assessed in terms of transition temperature with the accumulated data, and then incorporated into an empirical phase diagram (EPD) that provided an overview of CagL physical stability. These analyses indicated maximum CagL stability at pH 4-6 up to 40°C in the absence of excipient. Using this EPD analysis, aggregation assays were developed to screen a panel of excipients with some found to inhibit CagL aggregation. Candidate stabilizers were selected to confirm their enhanced stabilizing effect. These analyses will help in the formulation of a stable vaccine against H. pylori.
authors.affiliation: Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, Oklahoma, USA.
authors.forename: Shyamal P
authors.initials: SP
authors.lastname: Choudhari
authors.forename: Kirk P
authors.initials: KP
authors.lastname: Pendleton
authors.forename: Joshua D
authors.initials: JD
authors.lastname: Ramsey
authors.forename: Thomas G
authors.initials: TG
authors.lastname: Blanchard
authors.forename: William D
authors.initials: WD
authors.lastname: Picking
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry*; D016481:Helicobacter Infections / Q000517:prevention & control*; D016480:Helicobacter pylori / Q000737:chemistry*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D055550:Protein Stability; D013057:Spectrum Analysis; D013696:Temperature; D022223:Vaccines, Subunit / Q000737:chemistry
chemical_list: D001426:Bacterial Proteins; D022223:Vaccines, Subunit; C568315:cagL protein, Helicobacter pylori
keywords: light scattering (static); pH; physical stability; protein aggregation; protein formulation; stabilization; temperature; vaccines